Question: "What does the Bible say about hentai? Is looking at hentai / cartoon porn a sin?"

Answer:
It seems that the latest craze in internet pornography is hentai, which is Japanese for "perversion." It is cartoon-based pornography based primarily on "anime," which is a popular form of Japanese animation. The terms "manga" and "doujin" are often closely connected to "anime." Some attempt to justify viewing hentai using the excuse that it is not "real people," and/or it does not involve real people doing immoral things. The arguments go further to state that the Bible never condemns "art" as being sinful. After all, don't some famous pieces of art include nudity and/or graphic images?

So, what would the Bible have to say about hentai? The three primary divisions of sin, according to 1 John 2:16, are the lust of the flesh, the lust of the eyes, and the pride of life. Pornography, whether cartoon-based or not, definitely causes us to lust after flesh, and it is undeniably a lust for our eyes. Clearly, hentai forms of anime / manga / doujin do not qualify as what the Bible says we should think about: “Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable - if anything is excellent or praiseworthy - think about such things” (Philippians 4:8).

Hentai is not true, it is not noble, it is not right, it is not pure, it is not lovely, it is not admirable. Hentai is neither excellent nor praiseworthy. Just like all other forms of pornography, hentai is addictive (1 Corinthians 6:12; 2 Peter 2:19), destructive (Proverbs 6:25-28; Ezekiel 20:30; Ephesians 4:19), and leads to ever-increasing wickedness (Romans 6:19). Lusting after other people (whether real or imaginary) is offensive to God (Matthew 5:28). Continual viewing of hentai pornography demonstrates that a person has not experienced the saving grace of God (1 Corinthians 6:9).